Although fossil fuels still have a wide application and high demand, they have limitations due to their finite reserves. Also, the combustion of fossil fuels produces carbon dioxide, which contributes to global warming.
With the development of various large natural (shale) gas sources in many parts of the world and with the existence of other methane sources such as coal bed methane, methane hydrates, etc., the availability of extensive methane reserves is assured at least for this century. The conversion of natural (shale) gas into liquids, preferentially to methanol used for transportation fuels and source material for varied essential chemical products, is of great practical significance (Beyond Oil and Gas: The Methanol Economy, G. A. Olah, A. Goeppert and G. K. S. Prakash, 2nd Edition, Wiley-VCH, Weinheim, 2009). Currently, widely practiced steam reforming processes of methane generate syngas, CO:H2 with a ratio of 1:3. Additionally, dry reforming with carbon dioxide provides CO:H2 in a 1:1 ratio. To manage the needed energy requirement (endothermicity) of the steam reforming, several processes including tubular as well as autothermal reforming (ATR) using partial combustion have been developed and widely used (Concepts in Syngas Manufacture, J. Rostrup-Nielson and L. J. Christiansen, Imperial College Press, London, 2011) to produce varying syngas compositions. In ATR, partial oxidation of methane with oxygen is combined with the steam reforming in the same reactor. These processes involve multiple steps to adjust the needed syngas ratio, however, and also produce significant amounts of carbon dioxide or other oxidation byproducts, which need to be separated or disposed. A CO:H2 ratio of 1:2 is not produced a single step either in ATR processes or in any of the other reforming processes.
The present invention discloses a new way to utilize methane or natural (shale) gas sources to produce methanol and derived products to be used in the context of the “Methanol Economy”. Fossil fuel sources such as petroleum oil, natural gas and coal can be converted by known processes, including those disclosed in the patent applications of the present inventors, into methanol and dimethyl ether by bi-reforming, involving chemical recycling of carbon dioxide, the final product of their combustion use. Methanol and dimethyl ether are used as transportation fuels, as substitutes for gasoline and diesel fuel in ICE-powered vehicles with some necessary modifications to the existing engines and fuel systems, as well as in fuel cells. The storage and use of methanol, in contrast with hydrogen, does not require new infrastructure such as expensive pressurization and liquefaction. Because methanol is a liquid, it can be easily handled, stored, distributed and used in vehicles. It is also an ideal hydrogen carrier for fuel cells using a reformer and can be used in direct oxidation methanol fuel cells (DMFC). Dimethyl ether although a gas at room temperature, can be easily stored under modest pressure and used effectively as substitute for diesel fuels, liquefied natural gas (LNG) liquefied petroleum gas (LPG) and household gas.
In addition to use as fuels, methanol, dimethyl ether and their derived products have significant applications and uses. They are starting materials for varied chemical products. They can be catalytically converted into olefins primarily ethylene and propylene and their polymers. They are thus convenient starting materials for synthetic hydrocarbons and their products further replacing oil.
Methanol can also be used as a source of single cell proteins (SCP). SCP refers to a protein produced by a microorganism, which degrades hydrocarbon substrates while gaining energy. The protein content depends on the type of microorganism, e.g., bacteria, yeast, mold, etc. SCP's have varied uses, including as food and animal feed.
Considering the wide uses of methanol and dimethyl ether, it is clearly desirable to have improved and efficient new methods for producing them.